NEX - How do you which car to ride?

I've been conducting a lot of research for my upcoming trip to Tokyo. I've seen the time tables... I've studied the NEX maps... I know where to board it at Narita... I know that not all the departures go to Shinjuku... However, there are some small but important details I have not yet been able to find.

I'm arriving into Narita (NRT), and plan to take the NEX all the way to JR Shinjuku station. The part I still haven't figured out is the split at Tokyo Station. From all I have gathered, the train cars coming into Tokyo Station from Narita are separated at Tokyo Station, and are lead off by different trains towards the direction I want to head in (Shinjuku station) and the other towards Yokohama.

So, apparently the trick is to get on the right set of train cars while AT Narita. That's where most of the information stops.

How do you know which cars are heading towards Shinjuku and which ones will be split off for Yokohama? Are they marked at the loading point in Narita?

The only scrap I've managed to find was someone making the vague statement, ''the front ones go to Shinjuku''. Which front ones? How many of them? Do the positions of the cars going to Shinjuku station change? Will I see which cars are going where when I make my reservation on the NEX?

Any detailed information in this area would be greatly appreciated.

Thanks!

How do you know which cars are heading towards Shinjuku and which ones will be split off for Yokohama? Are they marked at the loading point in Narita?

Seat reservations are mandatory for riding the Narita Express. when making seat reservations, you will get a ticket with car and seat number printed on. Just match the car number on the ticket with the car number on the train and you will be safe.

I think I'm still missing a piece of the puzzle though. I understand that you have to make a seat reservation.

However, what I don't understand is how you know which cars are going to be heading towards Shinjuku station and which ones will be decoupled and sent to Yokohama after reaching Tokyo station.

Are you trying to say that when I am making my seat reservations I will be shown which cars are heading towards Shinjuku and can make my decision to be seated on that car? Or are you saying that everyone knows that as an example certain cars like the first half go to Shinjuku and the other half or go to Yokohama? If it is a known constant, which cars go where? If it changes, how do I find out?

My current understanding is that the NEX doesn't have a line that departs Narita that ONLY goes towards Shinjuku or Yokohama. My understanding is that all the NEX departures from Narita pretty much split at Tokyo Station.

So, figuring out which specific car/s I have to make the seating reservation in is pretty important. I've heard that there can be upwards of 12 cars coupled together that can leave Narita to Tokyo Station.

If I am misunderstanding how the NEX works, then please set me straight. I appreciate it.

Thanks!

When you get a seat reservation, you tell the ticket counter person that you want to travel from Narita Airport to Shinjuku. You will then be automatically assigned a seat in a car that travels to Shinjuku. All you have to do is to match the car number on your seat reservation ticket with the car number on the train.

That is exactly what I needed to know! Thank you very much!

When you make a seat reservation to Shinjuku, the seat reservation ticket you get will say which car you are sitting in. The train cars are numbered, (eg car 1, car 2, car 3 and so on). The reservation person will give you a seat reservation on a car that goes to Shinjuku, the car number will be indicated on the ticket, match it up with the car number on the platform.

If for some crazy reason you still become super lost (I really don't see how, especially at Narita Airport station), just look at the side of the train, the car will say "Narita Express X Shinjuku" plus a million announcements onboard then for whatever reason that still doesn't clear it up, ask someone on the platform.